Semi-automatic telephone system.



v E. D..FALES. SEMI-AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED SENT- 3, 19'2'.

Patentw Oct. 9. 1917.

4 SHEETS-SHEET 1- E. n. mes. SEMI-AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED SEPT-3, I912. 1,242, 164. Patented 0ct. 9, 1917.

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E. D. FALES.

SEMI-AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED SEPT. a. I9l2.

Patented 00 9,1917.

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E. D. FALES. SEMLAUTOFMHC'TELEPHONE .SYSTEMP APPLICATION FI LED SEPT. 33 I912: I

Patented Oct. 9,1917.

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' mumaleHw TTOR/S/Ek j EDWARD D. FALES, OF CHICAGO, ILLINOIS, ASSIGNOR T0 ATJTOMATIC ELECTRIC COM- PAN'Y, OF CHICAGO, ILLINOIS, A CORPORATION ILLINOIS.

$EMI-AUTOMATIC TELEPHONE SYSTEM.

Specification of Letters Patent. 5 Patented Get, 9, 1&1?

Application filed September a, 1912. Serial No. 718,335.

To all whom it may concern:

Be it known that I, EDWARD D. FALEs, a citizen of the United States of America, and resident of Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Semi-Automatic Telephone Systems, of which the following is a specification.

My invention relates to improved telephone systems, and more particularly to semi-automatic systems, and the Object is to improve the general elficiency of such a sys-' scribers in these distributed groups cannot obtain a connection with an operator at whose board there is an unanswered call. In this manner the traffic is more evenly distributed and more efiicient trunking obtained.

A further object is the provision of improved means whereby an operator at one board cangive orders to an operator at a second board. Ordinarily operators at one board all have direct access to an order wire which leads to each of the operators at the second'board. .With this arrangement several operators may get in .on the sameorder wire at the same time and thereby create a great deal of confusion. An object of my invention is to provide an automatic switch which has access to a plurality of order wires one of which leads to the operators talking circuit at each position on the second board and this switch is adapted to automatically select an idle operator. In this way all confusion is avoided.

These and other objects of my invention will be more readily understood by reference to the accompanying drawings, in which I have illustrated one embodiment of my invention.

In said drawings Figure l is a die. ram matic layout-of a telephone system em odying the principles of my invention.

Figs. 2, 3 and l taken -together represent a complete connection between afcalling telephone T and a called telephone T in the above system. 4

Fig. 5 represents the wiring of a portion of the master switch bank contacts.

In Fig. 1 there are represented. two manual switchboards'M and M. Associated with the board M there are shown five groups of subscribers stations A, A A A and A of terminating directly in the manual switchboard in answering acks in the usual manner, are each provided with an auto,-

matic trunk-selecting switch C. The switches C are divided into groups corresponding to the subscriber groupsA, A etc., each group having access to a plurality of trunk lines less in number than the subscribers in the group, which trunk lines terminate .in answering jacks J at the. switchboard. Although there is shown only one line leading fromeach'grouprof switches C to the switchboard, this line is assumed to be a cable containing as many separate trunk lines as there are shown j'abks J connected therewith at the switchboard. qThere are shown herein, therefore, three trunks for I each subscribers group. All of the trunk lines which are accessible to each of the groups of subscribers stations A, A and A terminate upon the same operators position of the switchboard. The trunk lines which are accessible to the subscriber groups A and A, however, are uniformly distributed among the different operators. For the purpose of being called, the subscribers in the groups A, A A ,.A" and A are provided with the usual multiple jacks J, not only in the switchboard M but also in the switchboard M. The subscribers in -the groups A and A, which are associated with the board M, are provided with trunking switches C in the same manner as the previous groups referred to. to which the subscribers A and A have access are distributed among the operators at the board M. Instead of-the usual multiple jacks, the subscribers in the groupsA and A are connected to the bank contacts of a 105 is provided with a multiple jack J 2 in-each 110 The subscribers lines, instead.

The trunk lines vidual order wire leads to an automatic trunk-selecting switch 1). The switches D have access to a plurality of circuits, one leading to each operators position at the board M The connection shown in Figs..2, 3 and 4C is assumed to be a connection between one of the subscribers of one of the groups A or A in the board M to one of the subscribers in one of the groups A or A at the board M, and involves all of the different'kinds of apparatus employed in the system. The telephone T may be of any suitable type ofmanual common battery telephone, and, as represented herein, comprises the usual receiver 2, transmitter 3, switch hook 4, ringer 5 and condenser 6.

The trunking switch C, which is individual to the line of the telephone T, is of the general type of line switch disclosed in British patent to R. W. James, No. 26,301 of 1906, being however, of the specific form shown in British patent to T. G. Martin, No. 1,419 of 1910. This type of line switch, as is well known, comprises a plunger (not shown) attached to a so-called plunger arm 7, which, when attracted by the magnet 8, causes its plungerto be thrust into some one o a plurality of groups of contact springs, each of which forms the terminal of a separate trunk line. The line switches C ofthe subscribers in the groups A and A (Fig. 1) should have self-alined plungers that is, their plungers, whenreleased from an operated position, should automatically restore into locking engagement with their common plunger guide shaft and, therefore, in alinement with all the idle plungers in the group, as shown in said British Patent No. 26,301 of 1906, rather than remain in front of the trunk terminal from which they were disengaged until they are subsequently picked up by the master switch. shown in said British Patent No. 1:419 of 1910. All the switches C of a group are controlled by a common mechanism or master switch F. The master switch F is of the general type of master switch disclosed in the British patents hereinabove referred to, being of a somewhat different construction from'either, however. In the form of master switc shown herein the usual plunger guide shaft 9 is connected with a rotary shaft 10 in such a manner that as said shaft 10 rotates in either direction the plunger guide shaft 9 is given an oscillating motion about the same as an The movement of the shaft 10 in one direction is produced by a solenoid 11, while the movement of the shaft in the other direction is produced by a spring 12. Attached to the shaft 10 there is a locking plate 13, said plate being provlded in its periphery with as many notches 14- as there are trunk lines to which the line switches C of the group controlled by the master switch have access. The notches 14 are adapted to cooperate with a locking dog 15, whereby the plunger shaft 9 may be locked with its plungers in front of any one of the trunk lines. The locking dog 15 may be withdrawn from the plate 13 by the energizatioirof the relay magnet 16. Secured to the shaftlO there are also two arms 17 and 18. When the plunger shaft reaches the limit of its travel in one direction, the arm 18 presses the spring 19 into engagement with the spring 20; and when the plunger shaft reaches its limit in the other direction, the arm 17 raises the spring 21 to unlock ,the springs of the relay23, which, at that time, will be held in their operated positions by the engagement of the spring 24 with the detent on the under side of the spring 21, as will hereinafter be explained. The master switch is also provided with the usual bank of contacts comprising the common segment 25 and a plurality of individual contacts a, one for'each trunk line. The wiper 26 is adapted to maintain the segment 25 in engagement with the individual contact of a trunk line before which the plungers of the idle switches are resting.

The trunk line leading from the group of switches C to the manual board terminates at the board in the jack 7' and is provided with the usual line lamp 27. The trunk circuit is provided with a plurality of circuit-controlling relays, the operation of which will be fully described hereinafter. The line lamp 27 is connected to ground through the winding of a pilot relay 28 which is common to all of the trunks lead.

ing into. a single operators position. The relay 28, besides controlling the circuit of the usual pilot lamp 29,.is provided with a plurality of contact springs, one of which is connected to the-master switch bank contact of each one of the trunk lines which leads to that operators position from the group of subscribers substations, such as the groups A and A (Fig. 1), which are the groups which have distributed trunk lines, The apparatus associated with the subscribers in the groups A, A and A (Fig. 1) may be the same in all respects as the apparatus associated with the subscribers in the groups A" and A except that there are no connections leading from their master switch bank contacts to the pilot relays 28 of the switchmemes hoard. Referring to Fig. 5, the manner in which the master switch bank contacts of the groups, such as the groups A" and A are connected to the pilot relays 28 is subscribers leads to one operators position,

that the second trunk line in each group leads to the second operators position, and

so on. The first contact in each of the four banks is, therefore, shown connected to a contact in the relay 28 of the first operators position. The second contact in each bank 1 is shown connected to a contact in the relay 28 of the second position, and so on.

The operators cord 0 (Figs. 2 and 3) 1s adapted for use at either of the boards M or M and is similar to the usual form of operators cord circuit. It comprises the plugs 32 and 32' connected together through the condensers and 31 and is provided with the usual calling and answering super- 'visory relays 32 and 33 and the lamps 34 and 35. At R (Fig. 3) there is shown one of the trunk lines which connects the two boards M and M (Fig. 1). This trunk is 1 board M (Fig. 1).

shown provided at one end with two multiple jacks 7' and 7' and terminating 'at the other end in a plug 10 Thistrunk-is provided with a supervisory lamp 36 and suitable relays for controlling the same. The

-' relay 38 is a polarized relay. Each operator at the board M is also provided with an automatic calling device of a suitable character for controlling the connector switches E, which calling device may be r connected with the cord circuit by meansof a key-k. The calling device is represented in Fig. 3 diagrammatically by a pail: of impulse springs 40. The callingdevice may be of the character shown in British patent j to S. G. S. Dicker, No. 29,654 of 1910, or

any other suitable construction canfb'e employed.

At is (Fig. 2) there is shown 'an prder wire key such as is located at the 'anual At S there is shown one of the operators sets of the 'manual board M (Fig. 1). At D is shown one of the automatic trunk-selecting switches by means of which idle order wires are selected.

The switcn D is the same in principle as the Subscibers individual switch .0 (Fig. 2). it, however, has no line relay, such as that which comprises the lower portion of the plural wound magnet 8 in the switch C. The witches D belonging to all the operators at the board M are controlled by a common master switch F whim is similar to the master switch F (Fig. 2). At Q there is shown a busy tone signaling machine.

Although only one jack 1' is shown in nector E (Fig. 4) is assumed to be of the type of connector switches represented in United States Letters Patent No. 815,176,

granted March 13, 1906,"to'Keith, Erickson and Erickson, the circuits being somewhat modified. however, so that the switch may be operated by impulses delivered over the two sides of the line in series, in a manner similar to that described in said British Patent No. 1,419 of 1910 above referred to. In general, the switch comprises a bank of contacts arranged in rows or levels which are adapted to be engaged by a set of wipers 43, 44 and 45 which are carriedupon' a vertically and rotatably movable shaft, the movement of which shaft is controlled by the vertical magnet 46 and the rotary magnet 245, Theusual side switch comprising the wipers 138, 47 and 48 is controlled by the private magnet 49 in: the usual and Well.-

known manner. The usual release magnet is represented at 50. The operations of the switch are controlled through the medium of a double-wound line relay 51 which is connected with the line through the springs of a reversing relay 52, which relay 52 is in turn controllable by the called subscriber through the medium of the so-called backbridge relay 53. The relays 54 and 55 are slow acting relaysthat is, relays which deenergize slowly after their energizing circuits have been. broken. The proper operation of these relays may be conveniently obtained by securing a heavy ring of copper or other conducting material around one end of the core. Y

The substation T and the line switch C may be in all respects the same as the substation T and the line switch C (Fig. 2), with the exception that instead of multiple jacks, the line of the substation T is provided with multiple contacts 56, 57 and 58 in a plurality of connector switches E.

Having given a general description of the apparatus, the operation by which the connection is extended from the telephone T to the telephone T will now be explained in detail. Upon the removal of the receiver from the switch hook at the telephone T, a bridge is closed across the calling line through thereceiver 2 and transmitter 3, whereby an energizing circuit is closed extending from ground G through the springs 60 and 61, telephone T, springs 62 and 63 and the line winding 64 to the battery lead 65, and thence through battery B to ground relay 72, springs 68 and 69, telephone T and back over the other side of the line through the springs 70 and 71 and the relay 7 3 to the battery lead 65. The relay 72, upon energizing, completes a circuit extending from ground G through the contact 7 4 and the relay 75 to the battery lead 65. The relay 7 5, upon energizing, completes a circuit extending from ground GR through the 'contacts 76 and ,the line switch bank springs 77 and 78 and the holding winding 79 of the switch G to the battery lead 65.. The energization of the winding 79 serves to maintain the switch G in its operated position after the line winding 64 is disconnected from the line upon the operation of the switch. There is a branch connection from the springs 78 in the circuit last traced hich extends to the sleeve contact of the multiple jacks of the calling line, whereby said jacks are provided with a busy test potential from the ground G The closure of the contact 80 upon he energization of the relay 72 completes a circuit extending from ground G in the right-hand end of the'trunk through the lower winding of the relay 81, contact 80 and impedance coil 82 to the battery lead 65. The relay 81, upon energizing, closes the circuit of the lamp 27, said circuit extending from ground G through the pilot relay 28, lamp 27, contact 83 and springs 8 1 and 85 to the battery lead 65. v

The closure of contact between the band springs 86 and 187 upon the operation-of the line switch 0 completes a circuit extending from ground G7 through said'springs, master switch bank contact 186, wiper 26 (which is assumed to be resting upon the contact 186 at the time), segment 25 and the relay 87 to the battery lead 65. The relay 87, upon energizing, completes a circuit extending from ground G through the contact 89 and the relay 16 to the battery lead 65. The relay 16, upon energizing, withdraws the locking dog 15 from the cam 13 and allows the master switch to rotate the plungers of the idle line switches to an idle trunk line. It will be seen that the relay 16 will remain energized and the master switch continue to operate until the wiper 26 finds the nongrounded terminal of the first idle trunk line, when the circuit of the relays 87 and 16 sition,

a short distance beyond said trunk, when the arm 18 on the master switch will press the spring 19 into contact with the spring 20, whereby a circuit will be closed from ground G through the springs 89 (bearing in mind that the relay 87, as well as the relay 16, is at this time energized), springs 19 and20, relay 23 and the contact 90 to. the battery lead 65. The relay 23, upon energizing, closes the contact between springs 21, 91 and 92, wherebya locking circuit is closed through the relay 87 and the energizing circuit of the solenoid 11 is closed. The springs of the relay become locked in their energized positions by the engagement of the spring 2 1 with the detent on the spring 21. solenoid 11, upon energizing, moves the plunger guide shaft and the idle .plungers back in the opposite direction until the arm 17 raises the spring 21 to unlock the springs of the relay 23, whereupon the circuits of the solenoid 11 and the relays 87 and 16 are broken and the plungcrs are brought to rest opposite the first trunk line, ready to begin their selecting operations over again.

It has been explained how, when connec tion is extended to the manual switchboard upon the operation of the line switch C, the circuit of the line lamp 27 is closed in series with the pilot relay 28. This not only lights the lamp 27, but the relay 28 is energized to close the circuit of the pilot lamp 29. It has heretofore been explained that the relay 28 is connected -in series with all the line' lamps, such as the lamp 27, of all the trunk lines entering any particular operators poand that the relay 28is provided with a contact for each trunk line which leads from the groups of subscribers whose trunk lines are distriluitcd among-the different operators, as shown at A and A in Fig. 1. In Fig. 2 only the contact of the relay 28 which is allotted to the trunk line illustrated is actually shown connected to its master switch bank contact 186. With this arrangement it will be seen that whenever any lamp 27 in any operators position is burning, or, in other words, whenever there is an unanswered call in that position, the pilot relay will supply a ground potential to the master switch bank contact of all the distributed trunks coming into that position, whereby no call will be permitted to that a call from any of the subscribers groups which have access to a plurality ofoperators' trunked to that operator immediately, even though there are one or more unanswered calls in her position already.

Upon receiving the signal of the lamp 27, the operator inserts the plug 2 into the jack j, whereby the calling subscrib ers connection is extended to the cord 0 and a circuit is closed. through the cut-off relay 93 of the r unk and the calling supervisory relay 32 f the cord. The circuit of the relay 93 exnds from ground G through the resistshoes 94: and 95, sleeve contacts of the plug grind the jack 7' and the relay 93 to the ttery lead 65. The relay 93, upon energizig'uig, destroys the circuit of the lamp 27 and ftlfle pilot relay 28 andconnects the battery Eead 65 with the upper winding of the relay 81. The relay 32 has two ehergizing circuits,

(one extending from'ground G through the lower winding of said relay, ring conductors of the plug 50 and the jack 7', contact 80 and the impedance coil 82 in the trunk to the battery lead 65. The other circuit extends from ground G at the cord relay 73 through the contact 96, relay 99, tip conductors of the jack 7' and the plug p and the upper winding of the relay 32 :to the batterylead 65. In its energized position the relay 32 maintainsthe circuit of the lamp 34: open and short-circuits the resistance 94:. The relay 99 in the cord, upon energizing, extends a second holding ground from ground G to the holding winding 79 of the line switch G.

Upon learning that a connection is desired with one of the subscribers who is called automatically from the board M, the operator at the cord 0 depresses her order wire key C The closure of the contact 101 of this key completes a circuit from ground G through said contact, conductor 102, pull-down winding 103 of the switch D, springs 104. and 105 and the contact 106 to the battery lead 65. The winding 103, upon energizing, draws down the plunger arm 110, whereby the operators order wire conductors 206 and 107 are extended through the contacts 108 and 109'to an idle operators set S at the board M. Upon the attraction of the plunger arm 110, the spring 111 is forced into contact withi the spring 104, and the spring 104 is carried out of contact with the spring 105, wherebyi the winding 112 is inserted in series with the winding 103, so as to cut down the 'holding current for the switch. 'The closure of the contact 113, upon the operation of th'e'switeh D,-

operators set S. In case there are more con-- tacts in the bank of the master switch F than there are operators sets S, the superfluous contacts may be permanently grounded, as -indicated at G, whereby the master switch will be driven past said contacts. If all the order wires are busy, all the contacts in the master switch-bank F will be grounded and the master switch will operate .continuously. During this operation the contact 106 will be open, thereby disconnecting the battery from all the idle switches D. The contact 115 will at the same time be closed, whereby the busy signaling machine Q is connected with the conductor 206 through the contacts 116 of the idle switches D. Therefore, any operator at the,board M who depresses her order wire key while there is no idle set S will obtain a busy signal. The operators who have actually operated their switches D to obtain connection with an order wire will receive no busy signal,-because the contacts 117 and 116 in their switches will be open.

Upon receiving an order for ajconnection over the order wire selected in the manner explained above, the operator at the board M assigns an idle trunk'line to an operator at the board M, whereupon the operator at the board M releases her key It and inserts the plug 2 (Fig. 3,) into the jack 9' of the trunk assigned. Upon the insertion ofthis plug a circuit is closed from ground G at the cord 0 through the springs 118 and 119,

'lamp 35, conductor 120, sleeve contacts of to the battery lead 65. The relay 121, upon energizing, closes the circuit of the lamp 36.

The plug p is then inserted into the jack j of a trunk line leading to a connector having access'to the proper group of sub-' scribers, and the key 70 is operated to connect the calling device 40 with the trunk. A circuit is thereby completed extending from ground G" (Fig. 4) through the lower winding of the connector line relay 51, back contact of the spring 122, trunk conductor 123, contact 124 of the key la, impulse springs 40, key contact 125, tip conductors of the plug 39 and the jack 3' trunk conductor 126, back contact of the spring 127 and the upper winding of the relay 51 to the battery lead 130. The relay 51, upon energizing, closes the circuit of the slow acting relay 54. The closure of the Contact 131 at the key is (Fig. 3) closes the circuit of the relay 132, which, upon energizing, forms a docking circuit for itself through its own relay 132 bridges the polarized relay 38' across the calling end of the cord R.

The operator at the cord R now operates her callin device for the two digitsof-the number 0 the called substation, which, in

this case, will be assumed to be 20. Upon the first operation of the calling device the impulse springs 40 are separated twice momentarily, whereby the connector line relay 51 is permitted to deinergize twice. The relay 54, being a slow acting relay, does not denergize upon the momentary interruption of its circuit by the relay 51. Therefore, each time the relay 51 denergizes an impulse of current is transmitted through the vertical magnet 46 in series with the slow acting private magnet relay 55. The magnet 46 operates in response to these impulses to raise the switch shaft and wipers two steps, while the slow acting relay 55 operates to close the circuit of the private magnet 49 and maintain it closed until after the last impulse is delivered. Upon the cessation of the impulses the relay- 55 deenergizes and breaks the circuit of the private magnet 49, whereupon it permits the side switch to pass to second position. The

, closed from ground G 'through said side switchwiper, shaft private wiper 45. bank contact 58 and cut-ofi winding 136 to the battery lead 130. ,The winding 136, upon energizing, attracts the armature 137, whereby the switch C is disconnected from the called line and the contact 238 in the talking circuit is closed. The current flowing through the winding 136 is not strong enough of itself to attract the arm'ature 237. In the circuit just traced there is also provided a guarding ground potential from ground G to all the connector private bank contacts corresponding to the contact 58 of the called line. Upon the movement of the side switch wiper 138 of the connector to third position, a circuit is closed from ground G through the interrupter 139, springs 141 and 142, ringing relay 140 and r the side switch wiper 133 to the battery lead 130. The relay H0 thereupon begins to operate. to intermittently connect the ringing current generator X with the called line to signal the called subscriber. After the operator has completed the operation of her calling device for the last digit, the key 70 is restored to its normal position,-whereby the calling device is disconnected and a bridge is substituted tlIGI'OfOI across the meme-a tor, is in the proper direction to maintain I the contact, 143 open.

Upon the response of the subscriber at the called substation T, said substation is provided with talking current over a circuit extending from ground G at the connector E through the side switch wiper 47, lower winding of' the relay 53, private magnet springs 144, ringer relay contact 145, wiper 44, hence over the line to and through the substation T and back over the other side of the line through the contact 238 at the switch G, connector wiper 43, side switch wiper 48, ringer relay contact 146, upper winding of the relay 53 and the side switch wiper 138 to the battery lead 130. The relay 53, upon energizing, closes the circuit of the relay at the contact 176. The relay 175, upon energizing, opens the circuit of the ringing relay and forms a locking clrcuit for itself at the contact 177 to prevent the ringing relay from becoming operative again when the called subscriber hangs up his receiver. The relay 53, upon energizing, also closes a circuit extending from ground G through the side switch wiper 47, reversing relay and the contact 147 to the battery lead 130. The relay 52, upon energizing, transposes the connection between the windings of the relay 51 and the trunk conductors 1-26 and 123. This latter operation causes a reversal of the current in the relay 33 (Fig. 3), whereby said relay is operated to close the contact 143. The closure of this contact provides an energizing circuit for the calling supervisory relay 33 at the cord 0, which, upon energizing, extinguishes the lamp 35 to signify to the operator that the called subscriber has answered.

It the called line had been busy, the connector switch ll would not have made connection therewith, as described above, and the calling subscriber would have been given the busy signal in a manner which is well known and which it is not thought necessary to describe herein.

Upon the termination of the conversation the operator at the cord 0 is given the usual calling and answering disconnect signals in the following manner: Upon the hanging up of the receiver at the calling substation the energizing circuit of the cord relays 72 and 73 is broken. The relay 72, upon dei nergizing, disconnects the battery from the ring side of the cord, while the rela 73, upon deenergizing, disconnects groun G from the tip sideot the trunk, but leavesiit grounded at G through the relay 148. The/relay 148 is a high resistance relay and does not per mit sufiicient current to flow through it and through the upper winding of the relay 32 in the cord to maintain the latter relay energized'. The relay 32, upon deenergizing, closes the circuit of the lamp 34 in series with the cut off relay 93 of the trunk. The high resistance relay 148 in the trunk, however, is energized and, by closing the con-' tact 149, furnishes a new holding circuit for the line switch C to prevent it from releasing until the plug p is removed from the jack y. When the called subscriber hangs up his receiver, the back-bridge relay 53 of the connector E deenergizes and permits the relay 52 to in turn deenergize, whereby the direction of current in the polarized relay 38 (Fig. 3) is restored to its original direction. The relay 38 thereupon operates to open the contact 143, whereby the energizing circuit of the callin supervisory relay 33 at the cord 0 (Fig. 2 is broken. The relay 33, upon deenergizing, reestablishes the cirnection with a trunk line, which may be the same as shown in Fig. 2, to signal his operator. The operator answers with a cord 0 and may then complete the connection either with a subscriber of the board M by plugging "directly into a multiple jack of one of the subscribers of said board, or connection may be completed with another subscriber of a board M throughthe medium of the cord 0, trunk R and the connector E in the same manner as whencthe subscriber at the telephone T was the calling subcuit of the lamp 35. Upon the simultaneousjtscriber.

glowing oi the lamps 34 and 35 the operator removes the plugs 72 and p from the jacks j and 3'", respectively. Upon the removal of the plug p from the jack j the circuit of the trunk relay 1 18 is broken and it deenergizes and removes the last holding ground from the line switch C, whereby said switch is permitted to restore to normal position. Upon the removal of the plug p from the jack 9" the circuit of the relay 121 of the trunk R is broken and said relay, upon denergizing, opens the circuit of the lamp 36. When the light 36 ceases to glow, the operator removes the plug p from the jack 7"", whereby the energizing circuit of the connector line relay 51 is broken. The relay 51, upon deenergizing,'destroys the holding circuit of the relay 54, which in turn deenergizes and closes the circuit of the release magnet 50, said circuit extending from ground G through the contacts 151 a and 152, magnet 50 and contact 153 (which is closed uponthe first vertical movement of the switch shaft) to the battery lead 130. The magnet 50, upon energizing, immediately restores the mechanism of the connector to normal position and allows the cut-off winding of the switch C to deenen gize, whereby all the apparatus employed in the connection is left in readiness for another call. a

In the above description of the operation oi establishing a connection between the telephones T and T the operation of all the apparatus which is required to establish connection between any of the two subscribers in Fig. 1 has been explained. For instance, if the subscriber '1 had desired a connection with some other subscriber in the switchboard M, the operator would simply have inserted the plug p. into one of the multiple jacks of thesubscriber called for and signaled the subscriber through the While I have illustrated and described one particular embodiment of my invention,

it is to be understood that I do not wish to be limited to the exact construction shown and described, nor to the use of switches of the character with which I have chosen to illustrate my invention, but that many changes will readily suggest themselves to those skilled in the art.

lVhat I claim as my invention is 1. In a telephone system, a plurality of groups of subscribers lines, a plurality of operators positions, trunk lines extending from one group to one operators position' and from a second group to a second operators position, trunk lines from a third group distributed throughout a plurality of operators positions, and a relay common to said trunk lines and controlled from a subscribers line in any groupfor prevent ing a subscriber in said third group fromobtaining connection with an operatorsrality of trunk; lines terminating in jacks on said board, automatic selecting switches for connecting said subscribers lines with a preselected one of said trunk l nes, and means for preventing seizure of a trunk extending to said operators board when a connection has been established with said board over a second of said trunks until atter the operator has answered said. last-mentioned call, said-inans common to sa d trunk lines and controlled from any subscribers line. I

4. In a telephone system, a groups of subscribers lines, a plurality of operators positions, trunk lines extending from said subscribers lines and distributed througlmut a plurality of said operators positions, and n'laster switches controlling a group. of said line switches for selecting a trunk extending to an idle operators position.

5. In a telephone system, a plurality of subscribers lines divided into groups, a plurality of operators positions, trunk lines extending from said subscribers lines and distributed throughout a plurality of said operators positions and terminating in jacks thereat-,'an operators plug adapted to be connected with one of said jacks in answering a call, an automatic selecting switch for connecting with apreselected idle one of said trunks to extend a connection from a subscribers' line to said operators position, means common to said trunk lines and controlled from asubscribers line in any group for placing a guardingwpotential on the other trunks leading to said operators position when said connection is established, and means for removing said guarding potential when an operators plug is inserted in said jack in response to the call.'. I

6. Ina telephone system, a plurality of subscribers lines divided into groups, a plurality of operators positions, trunk lines extending from said suhscril'iers lines and distributed throughout a plurality of said operators positions and terminating in jacks thereat, anoperatofs plug adapted to be connected with said jack in answering a call, an automatic'selccting switch for connecting with a preselected idle one of said trunks to extend a connection from a subscribers line to said operators position, a relay in said operators position common to said trunk lines and controlled from a subr'sribers line in any group, means for energizing said relay when said call is established to prevent a second call to said operators position, and means for deenergizing said relay upon.,the' response of the operator to thereby permit the secondieal'l.

'7. In a telephone system, a plurality of groups ofsubscribers lines, a plurality of operators positions, trunk lines extending from one group to one operators position pl iiirality 1,242,1iea

and from a second group to a second operators position, trunk lines from a third group distrilmted throughout a plurality of operators positions, and circuits and a relay for preventing a subscriber in said third group from obtaining connection with an operatmrs position at which there is an unanswered (-all, said relay common to all of said trunk lines and controlled from a subscribers line in any group.

8. In a telephone system, a group of sub-- scribers lines, a plurality of operators positions, trunk lines extending from said subscribers lines and distributed throughout said operators positions, a progressively movable switch under the control of said subscribers lines for preselecting an idle trunk, and circuitsand a relay for preventing. the trunk bein'g seized which extends to an operators position at which there is an unanswered call.

' 9.' In a telephone system, a plurality of subscribers lines, an operators boaid', a plurality of trunk lines terminating in jacks on said board, automatic selecting switches for connecting said subscribers lines with a preselected idleone of said trunk lines, and

lines and controlled from any subscribers lin for preventing seizure of a trunk extenc ing to said operators board when a connection has been established with said board over a second of said trunks until after the operator has answered said lastmentioned call.

10. In a telephone system, a plurality of groups of subscribers lines, a plurality of operators positions, trunk lines extending from said groups of subscribers lines and distributed throughout a plurality of said operators positions, a relay at each of said operators positions common to the trunks extending to said positions, circuits controlled. by said subscribers for energizing said relay when a connection is established .with one of its trunks, potential circuits and a control ling automatic switch controlled by the energization of said relay for preventing a second trunk extending to that position being seized,- and means for deenergizing said relay when the operator plugs in to answer.

the call.

Signed by me at Chicago, Cook county, Illinois, this 28th day of August, 1912.

EDWARD D. FALES. Witnesses:

J. NoRBY, E. A. Gnuoo.

J circuits and a relay common to said trunk 

